A vehicle includes various cables to transmit signal and or pipes to deliver fluids such as fuels, coolants, heating fluids. A conventional pipe retaining device includes an opening for insertion and removal of a pipe and a cap clipped on a body of the pipe retaining device to sealing the opening. Such pipe retaining device is used for pipes having a certain diameter and for fixing a single pipe. Chinese patent application CN203010021U discloses a pipe clamp device for pipes with different diameters. The pipe clamp device includes a first pipe clamp and a second pipe clamp connected with the first pipe clamp. Each of the first pipe clamp and the second pipe clamp includes a pipe clamp body and an auxiliary body connected with one end of the pipe clamp body. A groove is formed at another end of the pipe clamp body. A plurality of continuous ratchets are formed on one side of the clamp groove, and a plurality of teeth matched with the ratchets are formed on the auxiliary body. By changing a depth that the auxiliary body is inserted into the groove, the position of the teeth relative to the ratchets can be adjusted such that a clamping area defined by the main and auxiliary bodies is changed to adapt pipes with different diameters. However, it can be difficult and time consuming to insert the pipes into the pipe clamp device and to adjust the retaining area. Thus, there is need for a pipe retaining device with simple structures and easy adjustment features.